Refrigerating method and apparatus



Feb. 19, 1935. D, F. KEITH 1,991,944

- REFRIGERATING METHOD AND APPARATUS FiledOct. 29, 1928 7 Sheets-Sheet 1Feb. 19, 1935. D. F. KEITH REFRIGERATING METHOD AND APPARATUS Filed Oct;29, 1 928 7 Sheets-Sheet 2 lu z . z m m m 3 Feb. 19, 1935. D, 1,991,944

REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 Sheets-Sheet un I J I f O 3/ an-neuter, 3 map Feb. 19, 1935.

D. "F. KEITH -1,991,944

REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 Sheets-Sheet 4Feb. 19, 1935. D, n- 1,991,944

REFRIGERATING METHOD AND APPARATUS F ile'd. Oct. 29, 1928 7 Sheets-Sheet5 Feb. 19, 1935. I D. F. KEITH I 1,991,944

I REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 snets sheet 6Feb. 19, 1935. KEITH 1,991,944

REFRIGERATING METHOD AND APPARATUS Filed Oct. 29, 1928 7 Sheets-Sheet 7Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE Y 1,991,944REFRIGERATING METHOD AND APPARATUS Application October 29, 1928, SerialNo. 315,621

7 Claims.

This invention relates to improvements in refrigeration apparatus,particularly of the intermittent absorption class, an example of. whichwill be foundin my co-pending application Serial No. 242,574, filedDecember 2'7, 1927, that resulted in Patent No. 1,816,975, dated August4, 1931. The invention has to do, also, with a unique method ofrefrigeration.

In prevailing types of refrigeration apparatus of the class referred tothere is the disadvantage that the, relatively hot liquid refrigerantthat collects in the evaporator during the heating period raises thetemperature of the refrigeration chamber unduly and melts to a greateror less extent any ice that has been frozen by the evaporator during thepreceding cooling period.

Therefore, my present invention has for its broad object to providemeans for stabilizing the temperature of the refrigeration space orchamber of refrigeration apparatus of the intermittent absorption class,and particularly preventing the melting of the ice during the heatingperiod.

Pursuant to this broad object, the invention has as a more specificpurpose the provision of means that will prevent to any appreciableextent the transfer of heat from the evaporator to the refrigerationchamber during the heating peri odwhen the evaporator isaboverefrigeration temperaturebut will not interfere with the exchangeof heat from the refrigeration chamber to the evaporator during thecooling or evaporation period.

In the carrying out of my invention I desirably insulate the evaporatorfrom the refrigeration chamber and locate in said chamber a coolingvessel containing a volatile liquid, which may be termed the secondaryrefrigerant (as distinguished from the primary refrigerant that isdistilled over into the evaporator during the heating period andevaporates therein during the cooling or absorption period) whosevapors, by a suitable means of communication, are intimately subjectedto the temperature changes of the evaporator. Preferably the evaporatoris insulated also, to such extent as is practicable, from the coolingvessel so that the contents of the latter will be little affected by thewarmth of the evaporator during the heating period.

' There is a further advantage in insulating the evaporator from therelatively cool refrigeration chamber that will be readily appreciatedwhen it is remembered that the vapors of the primary refrigerantcondense during the heating period in the coolest wart of the system.When the evaporator is exposed to the temperature of the refrigerationchamber a certain amount of condensation occurs therein and raises thetemperature .of the surrounding air in the refrigeration chamber,whereas, by insulating the evaporator, it is caused to warm up quicklyat the beginning of the heating period and confine the condensation ofthe primary refrigerant vapors to the condenser.

So that the nature of my present invention may be better understood 1may mention at this time that, during the heating period, very little ofthe heat of the evaporator is transmitted to the secondary refrigerantin the cooling vessel because the evaporator is more or less effectivelyinsulated from said vessel, and, furthermore, the vapors of thesecondary refrigerant that have access to the evaporator are a poorconductor or transmitter of heat. Consequently, during the heatingperiod there is no appreciable action in the cooling vessel, theconditions being not conducive of vaporization of the secondaryrefrigerant, and little heat interchange takes place between thesecondary refrigerant in the cooling vessel and the refrigerationchamber of the apparatus. During the cooling period, however, the vaporsof the secondary refrigerant are condensed by intimate subjection to thenow relatively low temperature of the evaporator and the resultantcondensate drains back into the body of liquid in the cooling vessel.This condensation of the vapors results in a lowering of the pressure inthe cooling vessel, with 9. corresponding drop in the boiling point ofthe secondary refrigerant, and said refrigerant starts boiling,abstracting heat to promote such action from the refrigeration chamber,and this action continues during the entire cooling period.

Thus it will be seen that during the heating period, when the warmprimary refrigerant is collecting in the evaporator and practically noaction is taking place in the cooling vessel, the temperature of the airsurrounding said vessel is little affected and any ice that has beenfrozen in the refrigeration chamber is conserved; and during the coolingperiod, when the secondary refrigerant is boiling within the coolingvessel; there is a condition existing analogous to, or in fact identicalwith, that attending the evaporation of the primary refrigerant in theevaporator and as a result of this condition there is an abstraction ofheat from the surrounding air in the refrigeration chamber, It is foundthat, when the apparatus is properly designed and constructed andcertain liquids are used, as water and ammonia in the main portion ofthe system and ammonia in the cooling vessel, there is a very slightdifference between the temperatures of the primary and secondaryrefrigerants during the cooling period.

If desired, I may combine with the cooling vessel a receptaclecontaining brine that becomes chilled during a cooling period and tendsto stabilize the temperature of the cooling vessel during the subsequentheating period and further prevents melting of the ice.

Various embodiments of the invention by which the foregoing objects,with others hereinafter appearing, are attained, are illustratedin someinstances more or less diagrammatically in the accompanying drawingswherein Fig. 1 represents a sectional elevation of a refrigerationapparatus incorporating the invention; Fig. 2 is an enlarged sectionaldetail, taken in the same plane as Fig. 1, of the evaporator and coolingvessel, the present view showing certain structural details that areomitted from the former view for clearness; Fig. 3 is a sectionsubstantially on the line 3--3 of Fig. 2; Fig. 4 is a sectional detailon the line 4-4 of Fig. 3; Fig. 5 is a diagrammatic sectional elevationof an apparatus involving two separate and distinct refrigeration unitsthat operate alternately to maintain cool two intercommunicatingfreezing tubes that are common to both units; Fig. 6 (Sheet 2) is asection through the evaporators of two refrigeration units, like thoseillustrated in Fig. 5, the cooling vessel in this case consisting of asingle freezing tube that is maintained cool by the evaporators of thetwo units; Fig. 7 is a sectional elevation of an apparatus involvinganother form of cooling vessel and a brine tank or receptacle;

Fig. 8 is a section, on a somewhat larger scale; taken on the line 8-8of Fig. '7; Fig. 9 is a viewsimilar to Fig. 8 showing the same coolingvessel as is illustrated in Fig. 8 but with enclosed brine tanks orreceptacles; Fig. 10 is an embodiment of the invention wherein twoU-shaped cooling vessels or tubes are employed, this form incorporatinga further modification of the brine tank or receptacle; and Fig. 11 is asection on the correspondingly numbered line of Fig. 10.

,While, for illustrative purposes, I have shown my present inventionassociated with apparatus disclosed and claimed in my previouslymentioned Patent No. 1,816,975, it is to beunderstood that the presentinvention is not limited to such a construction. As will be obvious fromthe following description, it is applicable to various types ofintermittent absorption refrigerators.

Describing first the refrigeration system, exclusive of the coolingvessels or freezing tubes,

and the brine tanks or receptacles of my present invention, andreferring by like numerals to the parts common to the variousembodiments disclosed, including those illustrated in Figs. 5 and 6wherein two refrigeration units are employed, 1 designates a generatorabsorber, 2 an evaporator, 3 a delivery conduit that leads from thegenerator absorber to the evaporator, and 4 a return conduit by whichthe refrigerant vapors-are conducted from the evaporator to thegenerator absorber. Parts of the delivery conduit 3 constitute,respectively, a dehydrator 5 and a condenser 6, the former being shownas a portion of said conduit that is inclined downwardly toward thegenerator absorber from a point where it joins, through an abrupt drop,the inlet end of the condenser, while the latter is shown as consistingof a coiled portion of the delivery con- .is in the form of a bottle.

duit. Both the dehydrator and condenser are located within a' box orcasing 7, shown as equipped with a filling cap 8, and adapted topermanently contain, preferably to its full capacity, a cooling agent,such as water.

The delivery conduit 3 leads downwardly through the top of a gas dome10, that rises from the evaporator 2, and terminates adjacent the bottomof the evaporator, preferably within a sump 11 that is formed in thebottom wall of the vessel so that as long as practically any liquid ispresent in the evaporator it will seal said conduit against the escapeof the refrigerant vapors from the evaporator through said conduit.

The generator absorber may be equipped with heat abstracting veins 15,and it may be located in a vertical flue 16. The refrigeration chamberis designated 17 and it is enclosed by insulated walls 18. Theevaporator 2 is located within the upper portion of the refrigerationchamber and it is shown as having its top disposed within a recess inthe top wall of the chamber so that its upper portion and the gas dome10 are in some measure insulated from the refrigeration chamber.

Situated below the generator absorber is *a heating device which, in thepresent instance, consists of an oil'burner 20, preferably of theso-called wickless type, that receives fuel through a pipe 21 from a cup22 within which is adapted to be placed, in inverted position, a font orreservoir 23 which, in the present case, This font or reservoir ispreferably of such capacity as will accommodate just enough oil tosupply heat for initiating one cycle of operation of the apparatus sothat after the user lights the burner he need give it no further thoughtas the same will go out when the limited oil supply is exhausted.Obviously, gas, electric, or other heaters may be substituted for theoil heater so far as the present invention is concerned.

A siphon 25, for returning residue liquid from the evaporator to thegenerator absorber at the beginning of each heating period, leads fromthe bottom of the vaporator up through the top of the gas dome 10,thence laterally and downwardly, incidentally through the adjacent endportion of the delivery conduit 3, into the generator absorber 1. Itwill be noted that the return conduit 4 connects at one end with theupper portion of the gas dome 10 while its opposite end is extendeddownwardly through the top wall of the generator absorber and terminateswithin this vessel below the minimum liquid level therein which level isindicated by the dotted line a. A sleeve 27 is shown as surrounding theoutlet end of the conduit and is suitably supported within the generatorabsorber with its lower end spaced from the bottom wall of said vessel.

The system is hermetically sealed and contains a quantity of a suitablerefrigerant and an absorber or a solvent therefor which, for the presentpurpose, may be considered, respectively, ammonia and water. This aquaammonia, or other equivalent mixture of refrigerant and solvent, is whatis commonly referred to as the refrigerant liquor, and when all theliquor is present in the generator absorber 1 it stands at about thelevel indicated by.the dotted line b.

To start the apparatus in operation a reservoir 01' font .23, filledwith oil, is inverted within the cup 22 and the burner 20 is lighted.Considering now the embodiments of the invention wherein only onerefrigeration unit is employed, the amount of oil accommodated by thereservoir or font is intended to keep the burner in operationapproximately one hour before the oil supply is exhausted, and duringthis hour the temperature of the generator absorber is raised tosubstantially 300 F. Said hour represents the heating period, or theinterval of active heat. During this hour of active heat the pressurewithin the system rises to a value of-from 160 to 200 pounds, the mostabrupt rise occurring within the very early stages of the heatingperiod. On the cessation of heat-that is, after the fuel supply has beenexhausted-the temperature of the generator absorber and the pressure inthe system immediately start to drop.

During the heating period, the refrigerant in the generator absorber isdriven out of solution and in the form of vapor rises through thedelivery conduit 3 and while passing through the portion of said conduitthat constitutes the dehydrator designated by the reference numeral 5,all or a large percentage of the absorber vaporsin the present casewater vaporswherewith the refrigerant gas is situatedcondenses and flowsback into the generator absorber, the refrigerant gas continuing onthrough the portion of the conduit that constitutes the condenser 6 andcondenses therein, the resultant liquid refrigerantanhydrous ammonia inthis instance-being collected in the evaporator 2.

At the conclusion of this phase of the operation the evaporator containsits maximum amount of liquid, the level of which is indicated by theline 0, and this body of liquid may contain a relatively small amount ofthe absorbent or aqueous condensate, it being practically impossibletoobtain a complete dehydration of the refrigerant vapors. I

The cooling period starts with the cessation of heat and it continues onuntil the next heating period which, in the embodiments of the inventionincorporating asingle refrigeration unit, is substantially 23 hoursdistant. Each cycle, including a heating and a cooling period, consumesabout 24 hours. As previously stated, very soon after the heat isremoved from the generator absorber, the pressure within the systemstarts to drop abruptly. Under these conditions the liquid refrigerantor anhydrous ammonia in the evaporator starts to vaporize and, inpromotion of such vaporization, abstracts heat from the sur-- roundingair. Also, under the low pressure now prevailing in the system, theabsorbent or solvent in the generator absorber attracts the refrigerantgas through the return conduit 4. The passage of the gas from theevaporator to the generator absorber through the return conduit isassured by the fact that the discharge end of the delivery conduit 3 issealed by the liquid refrigerant in the evaporator, and this sealremains effective until the liquid level falls below the end of thedelivery conduit. As the refrigerant gas escapes from the discharge endof the return conduit it is instantly absorbed by the solution in thegenerator absorber.

During the early stages of the heating period, the pressure within thesystem rises very rapidly, and almost instantly this pressure becomespractically uniform throughout the system, including the'interior of thesiphon 4, the pressure, being communicated to the central portion of thesiphon through the intervention of the liquid that is present in andabout the legs of the siphon. That is to say, as the pressure rises ittends to equalize throughout the system and asa result thereof it forcesthe refrigerant liquor' approaches a state of continuity throughout thelength of the siphon with the result that a siphonic action isinstituted, the flow being in the direction away from the evaporator andtoward the generator absorber. This siphonic action continues as long asthere is any refrigerant liquor in the evaporator to supply the siphonor, in other words, until the evaporator is practically emptied of theliquor,

In cases where two refrigeration units are employed, as in theembodiments illustrated in Figs. 5 and 6, the units are operatedalternately; and, in size they may, though not necessarily, be of aboutone-half the capacity of the refrigeration apparatus of a single unitembodiment. In considering the operation of a double unit outfit, wherethe same incorporates two units of approximately half the capacity ofthose employed in a single unit outfit, and taking as a basis for suchconsideration a proportionately shorter I time interval than that usedin describing the operation of the single unit embodiment, the cycles ofoperation of the respective units of a double outfit are started abouttwelve hours apart, and the heating periods are of approximatelyone-half hour duration. It is also apparent that about themiddle of theeleven and one-half hour cooling period of each unit, when theevaporator is abstracting heat from the sur-' rounding air and thusperforming its refrigeration function, the evaporator of the other unitis warm for a period of something less than onehalf hour while therelatively hot refrigerant condensate is collecting therein.

While in actual practice the twenty-four hour cycle for single unitembodiments has been found convenient, it is to be understood thatcycles of any arbitrary duration may be decided upon, and the capacityof the apparatus altered where necessary tosuit the same, and where thedouble unit outfit is described above as incorporating individualrefrigeration units of approximately one-half the capacity of thoseemployed in a single unit outfit, this is only illustrative and may bechanged as desired.

I will next describe the means that constitutes the substance of thepresent invention, and which, broadly, had its conception in the thoughtof providing an enclosure containing a volatile liquid which is, at oneand the same time, ex-

.posed to the refrigeration space of the apparatus and to thetemperature changes of the evaporator, the same preferably serving toinsulate the evaporator from the refrigeration space or, at

One form of the invention is illustrated in Figs 1 to 4, where a shell30 surrounds and is spaced from the cylindrical evaporator 2 of therefrigeration apparatus, and disposed belowthe shell are two double wallcylinders 31, which enclose cavities that are open at their forward endsfor the insertion and removal of ice trays 32 within which liquids ormixtures may be placed for freezing. Though this constitutes no,part ofmy invention, it may be explained that the ice trays may be divided byremovable partitions 33 for forming ice cubes, which is in accordancewith common practice. Because of their function, the cylinders 31 areordinarily referred to as freezing tubes. respective cylinders 31 aresealed at their forward ends while at their rear ends they communicatewith each other, through a tube 35, and with the space between theevaporator 2' and the shell 30 through a branch tube 36. The shell 30,the cylinders 31, and the tubes 35 and 36 may be considered together asthe enclosure or cooling vessel that contains the volatile liquid hereinreferred to as the secondary refrigerant and which is subjected to thetemperature changes of the evaporator and exposed to the refrigerationspace. Any one of several kinds of liquids may be used in the coolingvessel or enclosure, but I find that anhydrous ammonia is especiallysuitable when aqua ammonia is employed as the primary refrigerant of thesystem. The liquid normally stands in the cooling vessel at about thelevel indicated by the line d in Fig. 2.

In operation, while the relatively hot primary refrigerant is collectingin the evaporator,--the same being conveyed thereto by the deliveryconduit 3 from the condenser 6 above-the evaporator becomes warm and,inasmuch as its temperature is above that of the vapors of the secondaryrefrigerant in the cooling vessel, it has little effect thereon, andobviously less upon the liquid itself that is present in the cylinders31 because, first, said vapors are a poor conductor of heat and,secondly, the evaporator is more or less effectively isolated from thecylinders 31. Consequently, there is little or no action going on in theenclosure or cooling vessel during this time and very little heatexchange between the secondary refrigerant and the refrigeration spaceof the apparatus and the ice in the ice trays.

As soon, however, as the cooling or absorption phase of the cycle ofoperation begins, when the relatively pure primary refrigerant in theevaporator 2 (anhydrous ammonia, for example) starts to vaporize andpass back in gaseous form through the return conduit 4 to the generatorabsorber l where it is absorbed by the solvent therein, the evaporatorcools and condenses the secondary refrigerant vapors that are in contactwith its exterior and the resultant condensate drips from the evaporatorand drains back through the tubes 36 and 35 into the body of liquidcontained in the spaces between the walls of the cylinders 31. Thiscooling and condensing of the vapors causes the pressure within theenclosure or cooling vessel to drop with the effect that the boilingpoint of the secondary refrigerant also becomes lower whereupon saidrefrigerant starts to boil under the influence of the relatively warmsurrounding air in the refrigeration space. This results in thesecondary refrigerant continuing to abstract heat from the surroundingair for the promotion of its vaporization, and the vapors rise from theliquid body of the secondary refrigerant up through the tubes 35 and 36into the space between the evaporator and the shell 30 and condense uponthe evaporator and drip back into the body of liquid, as aforesaid, andthis action is uninterrupted as long as the primary refrigerantcontinues to vaporize.

The spaces between the walls of the Thus it will be seen that, in mypresent invention, the secondary refrigerant acts in precisely the samemanner during the cooling period as the ordinary refrigerant acts duringthe same phase of the operation in prevailing refrigeration apparatus ofthe intermittent absorption type. Upon initiation of the succeedingheating or condensing period, however, the evaporator becomes warm andthe vapors of the secondary refrigerant cease to condense and action inthe, enclosure or cooling vessel subsides and conditions remainsubstantially dormant therein until the next cooling or absorptionperiod.

The shell 30 and the space between it and the evaporator2'serve toinsulate the evaporator from the refrigeration space or chamber 17, andto further this end the top portions of the shell and evaporator areembedded within the top wall of the refrigeration chamber.

As a structural refinement, the portion of the shell 30 below the topwall of the refrigeration chamber, and the cylinders 31, are enclosedwithin a box-like metal casing 40 that is shown as secured to the topwall of the refrigeration chamber; and to more effectively insulate theevaporator 2 from the cylinders 31 and from the refrigeration space orchamber 17, insulating shields 41, which may consist of slabs of cork orother suitable material, may be disposed about the shell 30. Thesestructural details are shown in Figs. 2, 3 and 4, but are omitted forthe sake of clearness from the more or less diagrammatic view of Fig. 1.In furtherance of this insulation of the evaporator'2 from the body ofliquid in the cylinders 31, a radiation shield or baffle 42 may besuitably supported across and in spaced relation to the end of the tube36 where it joins the shell 30, the same beingshown in Fig. 3. It willbe understood that the front wall of the casing 40 has openings thatregister with the cavities of the cylinders 31 for the passage of theice trays 32.

In the modification of the invention illustrated in Fig. 5, where tworefrigeration units cooperate to maintain the refrigeration space orchamber of the apparatus cool, the evaporator 2 of each apparatus isenclosed by a shell 30, which is 'spaced a suitable distance from thewall of the evaporator, and the space between the evaporator and shellcommunicates through a tube 36 with the space between the inner andouter walls of a double wall cylinder 31 therebelow. The annular spacesof the two double wall cylinders, in turn, communicate through a tube 35The operation of this embodiment of the invention will be readilyunderstood from the foregoing description of the first embodiment,though it may be explained briefly that the two refrigeration units areheated alternately at intervals of approximately one-half cycle apart.That is to say, each unit goes through its heating and condensing periodat about the middle of the cycle of operation of the other unit.Consequently, there is a condensing of the secondary refrigerant goingon allof the time, so that the cooling vessel is continuouslyfperformingits refrigeration function, notwithstanding the fact that at intervalsone of the evaporators is warm and is not condensing the secondaryrefrigerant vapors during a relatively brief period of time. The partsare so arranged that the secondary refrigerant condensate drains fromthe shells 30 into the cylinders 31. l

Fig. 6 is a detail of an embodiment which m be identical with that ofFig. 5 excepting for the fact that here only one double wall cylinder isused, the same being designated 31. Shells 30 surround the evaporators 2of the refrigeration units, and the spaces between the shells 30 and therespective evaporators communicate with the space between the inner andouter walls of the cylinder 31 through pipes 35 and 36 The operation isthe same here as in the form last described.

Figs. 7 and 8 illustrate a form of the invention in which a shell 45surrounds the evaporator 2 and constitutes the enclosure or coolingvessel that contains, to about the level indicated by the line e, avolatile liquid that forms the secondary refrigerant. Situated withinthe lower portion of the shell 45 and having its forward end extended asuitable distance beyond the corresponding wall of the shell is a.freezing tube 46 for the accommodation of an ice tray 47, the front endof the freezing tube being open for the insertion and withdrawal of thetray, it being understood that the open end of the tube is, in practice,pre sented toward the door of the refrigeration space or. chamber 17.Suitably supported within the shell 45 and immediately beneath theevaporator 2 is a radiation shield 48 that is shown as following thegeneral contour .of theevaporator, even to the inclusion of a depression49 that accommodates the sump 11, the depression having a drain opening50 at its lowest point. The action here is the same as in the previouslydescribed embodiments, the vapors of the secondary refrigerantcondensing upon the wall of the evaporator 2 during the cooling periodand dripping therefrom onto the shield 48 and draining down the same andthrough the opening 50 to the body of liquid in the bottom portion ofthe shell 45, this action continuing throughout the entire coolingperiod, and the secondary refrigerant extracting heat from thesurrounding space and that within the tube 46 the while this vaporizingand condensing of the secondary refrigerant continues. As soon as theheating period is started, and the evaporator becomes warm, all actionwithin the shell 45 ceases.

Shown associated with the present form of the invention is a tank orreceptacle that is in the form of a drum 55, the same containing'aquantity of brine, the level of which is-indicated by the line ,1. Thepurpose of this is to intercept any heat exchange between the coolingvessel and the refrigeration space or chamber during the heatingperiods, thereby to stabilize the temperature of the latter.

A modification of the brine tank feature of the invention is illustratedin Fig. 9 where the same is shown associated with a form of coolingvessel like that illustrated in Figs. '7 and 8. The corresponding partsof the two embodiments-that is, the ones illustrated in Figs. 7 and 8 onthe one hand and in Fig. 9 on the other-insofar as they, pertain to theevaporator and cooling vessel, are designated by the same referencecharacters. In Fig. 9, two containers 56, shown as triangular incrosssection, are situated within the lower por-' tion of the shell 45on OPDOSltG SIdBS of the freezing tube 46. These are closed containersand have permanently sealed in" them a quantity ofv brine. The brinebecomeschilled during the cooling period, and during the heating periodserves to stabilize the temperature of the surrounding secondaryrefrigerant. I,

In Figs. 10 and 11, there are shown two cooling vessels or enclosuresfor the secondary refrigerant 'and each is designated 60 and is in theform of a U-shaped tube that is closed at both ends, one of the legs ofthe respective vessels being disposed within the evaporator 2 while theother leg is enclosed within the upper portion of a brine tank orreceptacle 61. In this case, the freezing tube 62 is incorporated in thelower portion of the brine tank and opens through the front wall thereofso that an ice tray 63 can be placed within and removed from said tube.The upper portion of the evaporator is embedded within the top wall ofthe refrigeration space or chamber, while its remaining portion, andparts of the cooling ves-= sels 60 between the evaporator and the brinetank 61, are encased within a covering 64 of insulating material.

The normal level of the secondary refrigerant in the vessels 60 isindicated by the line 9, in Fig. 10, and during the cooling period thevapors of said refrigerant that are present in the upper portions of thevessels 60 are condensed on the walls thereof .and drain back to thebodies of liquid in the lower portions of the vessels, the condensationcausing a lowering of the pressure in the vessels and a consequentiallowering of the boiling point of the secondary refrigerant so that saidrefrigerant boils and extracts heat from the brine within the tank 61,there being, in turn, a corresponding heat exchange between the brineand the air within the refrigeration spaceor chamber wherein the tank islocated. During the heating period there. is practically no actiontaking place in the vessels 60 and no appreciable heat interchangebetween the secondary refrigerant and the contents of the brine tank 61and consequently the brine will remain cool excepting as it may beaffected by conditions within the refrigeration space or chamber. Therefrigeration space or chamber is protected from the heat .of theevaporator 2 and the cooling 'vessels 60 during the heating period bythe covering 64 of insulating material.

If desired, brine tanks may be incorporated in the forms of theinvention illustrated in Figs. 1 to 6, where the. sameare shown indot-anddash lines and designated '70.

Having thus described my invention, what I claim is:--

1. In refrigeration apparatus of the intermittent absorption type, incombination with the evaporator, a shell spaced from the wall of theevaporator and forming therewith a chamber, a vessel in heat exchangingrelation to the refrigeration space of the apparatus and whose interioris in communication with the aforesaid chamber, the shell and ,vesselforming a sealed enclosure, said vessel containing a volatile liquid andso positioned with respect to said chamber that vapors of said liquidwhen condensed upon the wall of the evaporator will return by gravity tothe body of liquid in the vessel, and a radiation shield protecting thebody of liquid from the temperature of the evaporator.

2. In refrigeration apparatus of the intermittent absorption type, incombination with the evaporator and the refrigeration chamber, thelatter having an insulated top wall, a shell surrounding the evaporatorand having its upper portion embedded within said top wall, a doublewall freezing tube situated below said shell, the space between whosewalls contains a volatile liquid, anda conduit through which said spacecommunicateswith the space between the shell latter having an insulatedtop wall, a shell surrounding the evaporator and having its upperportion embedded within said top wall, a double wall freezing tubesituated below said shell, the space between whose walls contains avolatile liquid, a conduit through which said space commu nicates withthe space between the shell and evaporator, and a casing enclosing theshell and freezing tube and having an opening registering with thecavity of said tube for the passage of an ice tray.

v4. In refrigeration apparatus of the intermittent absorption type, incombination with the evaporator, a shell spaced from the wall of theevaporator and forming therewith a closed chamber, the lower portion ofsaid chamber containing a volatile liquid, and a radiation shielddisposed between the evaporator and said liquid.

5.. In combination with a plurality of refrigeration units of theintermittent absorption type that operate in rotation, each having itsindividual evaporator, a shell surrounding each evaporator, an enclosurein heat exchanging relation to the refrigeration space of the apparatus,and a conduit through which said enclosure communidenser, bothcondensation and evaporation tak-.

ing place at substantially the same pressure.

7. Refrigerating apparatus including a closed fluid circuit comprising aplurality of condensers and an evaporator and connections between saidcondensers and said evaporator, and means for alternately cooling saidcondensers whereby liquid refrigerant continuously evaporates in saidevaporator and condenses alternately in said condensers, the condensersand the evaporator being maintained at substantially the same pressure.

DAVID FORBES KEITH.

